Deep fryers are one of the most useful and popular devices in the commercial kitchen. Deep fryers have been used for years to make french fries, breaded foods, and specialty pastries. Their highly efficient and uniform heat transfer rate results in fast, accurate, and economical cooking.
The modern deep fryer consists of a large well or heating chamber which is filled with cooking oil. The cooking oil is heated to between 350 degrees to 400 degrees F. by electric resistance heaters inside the well or gas fired burners located below the heating chamber. Food items to be cooked are placed in wire baskets and lowered into the hot oil to a point of total submersion. Due to the high efficiency of liquid-to-solid heat transfer as well as the high ratio of hot oil volume to cool food volume, heat is rapidly transferred from the hot oil into the cool food product. This rapid and even heat transfer tends to produce a crisp outer surface while heating the foods inner core. The crisp outer food surface acts to seal the food while the moisture on the interior of the food is rapidly increased in temperature effectively steaming the inside of the food. This results in cooked foods such as french fries, fried chicken, or donuts which are crisp on the outside and moist and hot on the inside.
The flavor and unique texture of deep fried foods are key to their popularity. Inherent in this cooking method is a tendency for the food items to absorb a percentage of the oil in which they are being cooked. The amount of oil absorbed into the food can be somewhat reduced by adjusting the oil type and temperature, however, even under the best circumstance, some oil is absorbed into the food. This absorbed oil substantially increases the fat content of the food. High fat content is undesirable in foods. As a result, fried foods are linked to obesity and other health problems.
To eliminate the oil absorption problem, various methods of air frying have been created. Air frying consists of a stream of hot air into which the food product is introduced. The heat transfer efficiency of air-to-solids is lower than the heat transfer efficiency of liquid-to-solids. In an effort to improve heat transfer, a thin coat of oil is typically added to the surface of the food before heating. The oil acts as a heat transfer medium more efficiently coupling the hot air to the cooler food product.
The hot dry air which is used to satisfactorily heat the food causes moisture to evaporate from the food product. Air fried foods typically have a dry outer surface which is less crisp than deep fried foods. Moisture also tends to evaporate from the core of the food as the surface is heated. As a result, due to its poor texture and less desirable taste, air fried foods have not found the level of acceptance typical of deep fried food. New food products have been developed in an effort to overcome the deficiencies of air frying but none has equaled the acceptance of deep fried foods.
In an effort to gain the advantages of liquid-to-solid heat transfer while avoiding the disadvantages of food absorption of the liquid, various submersion barrier cooking techniques have been developed. Submersion barrier cooking requires the food item be held in a container, the container thereafter being submerged into the heated liquid. In theory, the container is fabricated of a material whose heat transfer rate is sufficiently efficient to not appreciably degrade the transfer of heat from the heated liquid to the food. However, in practice, prior attempts at submersion barrier cooking have failed to produce a cooked food product which equals the taste and texture of that produced by traditional deep frying.
Accordingly, there remains a continuing need for improved methods to isolate a food product from the cooking liquid yet continue to maintain the flavor and texture of that produced by traditional deep frying. The present invention fulfills this need, and further provides related advantages.